The present invention relates to a method and apparatus for producing expanded clay and expanded shale of the type set forth in my U.S. Pat. No. 4,324,554, where a straight-line continuous rotary tubular kiln is provided having charging and discharge ends, a stationary burner disposed in the vicinity of the discharging end and an additional mantle burner which rotates together with the kiln, wherein the raw material introduced at the charging end passes through a preheating zone heated by the mantle burner so as to dry and heat the raw material which is then expanded into the finished product in an expansion zone leading to the discharge end by means of heat generated by the stationary burner.
The present invention furthermore relates to an apparatus for implementing such a method for producing expanded clay and expanded shale in a straight-line rotary kiln of the type described above.
The process and the apparatus according to U.S. Pat. No. 4,342,554 has as one of its objects the saving of heat energy while simultaneously reducing heat requirements and apparatus cost.